The aims of this investigation are 1)to demonstrate the existence and distribution of Calcitonin Gene-Related Peptide (CGRP) in the opossum sphincter of Oddi (SO) and duodenum (DUO); 2)to quantitate SO and DUO tissue and plasma levels of CGRP and 3)to characterize the response of the in vitro SO to increasing concentrations of CGRP. Uses CDMAS only.